(1) Field of the Invention:
This invention relates to a novel heterocyclic derivative of formula (I): ##STR5## wherein R.sub.1 represents ##STR6## and R.sub.2 represents a hydrogen atom or an acyl group; its preparation; and radiosensitizing agents and antiviral agents comprising the derivative as their active component.
(2) Description of the Background Art:
Hypoxic cells in tumor tissues are strongly resistant to radiation. This fact is considered to be one of key factors that explains the obstinacy or recrudescence after radiotherapy. In view that hypoxic cells do not exist in normal tissues, it is very important to enhance the radiosensitivity of the hypoxic cells in tumor tissues in order to obtain better results from radiotherapy.
Meanwhile, viral infectious diseases which attack mammals including humans are contagious and bring agony and economic loss to our society. Only limited viral infectious diseases are curable by currently available antiviral agents, and new synthetic antiviral agents stand in demand.